In a number of medical procedures it becomes necessary to deliver material to a desired location. For example, in connection with many cancer treatments, particularly treatments to bones inflicted with cancer cells, it is desirable to deliver materials, usually in injectable form, to particular locations within the bone. In other instances, particularly when use of bone screws is desirable, materials, also usually of an injectable form, often need to be delivered to aid in fixation of the screw.
In the context of the present invention, as will be discussed in greater detail hereinbelow, the present inventors have discovered methods and apparatus which offer advantages over currently known methods and apparatus useful in the administration of such materials. For convenience of explanation and illustration, the present invention will be described in conjunction with various applications, but principally, bone screw and drug or other medication delivery systems. It should be appreciated, however, that various other applications and embodiments will be apparent in light of the following disclosure.
In the context of bone screws, as is known, bone screws may be attached to bones for any number of reasons, but generally such screws are attached for the purpose of repair of the weakened bone structure to support bones or bone structure which have become broken or weakened. In many cases, the brake or weakening of the bone is in whole, or at least in part, due to disease. That is, the bone breaks or weakens as a result of disease, e.g., osteoporosis. Current techniques, in general, do not take into consideration that condition in the context of the repair. Stated another way, the technique used to repair bone often fails to address the situation under which the bone broke or weakened in the first place.
For example, in accordance with conventional methods of attaching bone screws to bones, bone cement (typically an acrylic resin material) is injected through a pilot hole drilled into the bone prior to inserting the bone screw. After the bone screw is inserted into the site, the bone cement theoretically hardens to strengthen the fixation site. This method, however, lacks control over the location or amount of bone cement applied. For example, it is often difficult to control the placement of adhesive near tissue regions, specifically in the spinal cord region, and improper placement can result in injury. Moreover, too little bone cement or improper placement of the bone cement may result in a weak fixation site, which may lead to undesirable extraction of the bone screw from the fixation site. For example, if the bone has been broken due to, in whole or in part, a medical condition, the use of cement in this fashion may not materially enhance fixation. Specifically, if the bone is weakened due to, for example, osteoporosis, then merely adding an adhesive to the area, particularly if applied in a weakened area, may not address the pre-existing condition.
Moreover, in some cases use of the adhesive in this conventional manner can result in even more deleterious effects. Consider, for example, the case in which the adhesive begins to cure before, or during the insertion of the screw. In such a case, instead of enhancing the fixation of the screw, the adhesive may actually bind to the distal end of the screw, and, as the screw is inserted, cause further damage to the already weakened bone. Such effects, of course, may not be immediately detectable. That is, in some cases, while an initial "fix" may be obtained, the overall weakening of the fixation site may result in a weakening of the attachment over time, or in the best of cases, simply not aid in securing long term fixation.
Various bone screw configurations are known. For example, cannulated screws are known and typically used for such conventional applications. Alternatively, such cannulated screws are also utilized in connection with various pressurizing techniques. In connection with these techniques, suction is used to suck (i.e., withdraw) the blood and fat out of the bone canal. For example, in U.S. Pat. No. 5,047,030 issued Sep. 10, 1991 to Draevert, a suction drainage bone screw is described. The screw described is used initially to withdraw the blood and fat from a region surrounding the screw, such as by use of suctioning. While described as an advantage over existing pressurizing techniques, in all of the disclosed embodiments the removal of material is an important, if not essential aspect of the screw's success.
As described in the '030 patent, the bone screw is used to suck blood, fat and bone marrow out of the bone canal and its vicinity for suction drainage in the application of bone cement. Specifically, as described in the '030 patent, a cannulated bone screw is anterolaterally inserted into a distal tip of the prosthesis into a cortico-spongious plug, to ensure that the distal and proxible medullary canal remain delimited from the screw by means of the filter. The bone is then filled with bone cement, mixed under vacuum but pre-compressed prior to introduction to the bone, i.e., femur. In accordance with the disclosed embodiment, the bone cement is sucked deep down into the femur by the vacuum applied via the distal cannulated bone screw. Once a prosthesis component is inserted, the distal vacuum lead is pinched off and the vacuum then proximately applied until the cement has hardened.
The '030 patent specifically teaches against the use of bone cement under the so-called bone lavage and high pressurizing technique due to the disclosed number of fatalities resulting from such use. The method disclosed in the '030 patent and the devices used are complex. There thus exists a long felt and unresolved need for a bone screw and method of use of the same which overcomes the disadvantages of the prior art.
Moreover, the screw of the '030 patent, in accordance with one of its preferred embodiments, includes a number of radially extending transverse canals denoted by the numeral 4 in the '030 patent. As described in the '030 patent, the bone screw preferably exhibits several transverse canals, preferably 2 to 9 and more preferably 4 to 6 which contact the longitudinal canal. These holes are disclosed as enabling further increase in the effect of the partial vacuum. The use of numerous radially extending apertures, particularly in the fashion shown in the '030 patent, has the potential deleterious effect of reducing the integrity of the screw itself, i.e., weakening the screw.
Various drug delivery devices are also known, for example in the '030 patent, the screws disclosed therein are described as also having drug delivery capabilities. Nevertheless, the drug delivery capabilities are minimized by the potential lack of integrity of the screw itself and such screws do not offer advantages particularly for re-use which may be desirable in numerous cases.
Suffice it to say that numerous disadvantages exist with currently known methods and apparatus for delivery of material to a desired location. There is thus a long felt need to address these disadvantages through use of a device which is relatively easy to make and use.